Before the bell:

U.S. stocks were set to open lower Monday, after Japan's leading stock index plunged in reaction to the damage from last week's massive earthquake and tsunami.

The Nikkei ended down 6.2%, the index's biggest one-day drop since late 2008.
U.S. stocks ended higher Friday, despite news of the massive earthquake and tsunami in Japan. But all three major indexes ended lower for the week -- a week that included the ongoing civil war in Libya and planned protests in Saudi Arabia. The Dow and S&P 500 fell more than 1%, while the Nasdaq sank almost 2.5%.
World markets:

Companies: The U.S.-traded shares of some companies based in Japan were down sharply in premarket trade Monday.
Shares of Canon (CAJ), based in Tokyo, were down more than 6% in premarket trading. Toyota (TM) shares were off 7.5% early Monday, while Sony (SNE) was down 8.4%.
Early Monday, Warren Buffett's Berkshire Hathaway (BRKA) said it would acquire Lubrizol for $135 per share in an all-cash transaction. That's a 28% premium over Lubrizol's closing price Friday. The deal, valued at approximately $9.7 billion, is one of Berkshire's biggest acquisitions ever.
Shares of Berkshire (BRKB) edged lower, while Lubrizol's (LZ) stock jumped almost 27% in premarket trading.
With oil prices under pressure, airline stocks could gain some attention during Monday's trading day. Shares of Southwest Airlines (LUV) were down more than 5.4% in premarket trading.
Oil for April delivery slipped $1.52, or 1.5%, to $99.64 a barrel on concerns about the fallout from Japan's earthquake.
Gold futures for April delivery added $4.90, or 0.3%, to $1,426.70 an ounce.
The price on the benchmark 10-year U.S. Treasury was little changed, with the yield holding at 3.39%.